/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.camunda.bpm.extension.reactor.projectreactor.io.codec;

import org.camunda.bpm.extension.reactor.projectreactor.io.buffer.Buffer;
import org.camunda.bpm.extension.reactor.projectreactor.io.buffer.Buffer.View;

import java.util.function.Consumer;
import java.util.function.Function;

/**
 * An implementation of {@link Codec} that decodes by splitting a {@link Buffer} into segments
 * based on a delimiter and encodes by appending its delimiter to each piece of output.
 * During decoding the delegate is used to process each segment. During encoding the delegate
 * is used to create a buffer for each piece of output to which the delimiter is then appended.
 *
 * @param <IN>  The type that will be produced by decoding
 * @param <OUT> The type that will be consumed by encoding
 * @author Jon Brisbin
 * @author Stephane Maldini
 */
public class DelimitedCodec<IN, OUT> extends BufferCodec<IN, OUT> {

  private final Codec<Buffer, IN, OUT> delegate;
  private final boolean stripDelimiter;

  /**
   * Create a line-feed-delimited codec, using the given {@code Codec} as a delegate.
   *
   * @param delegate The delegate {@link Codec}.
   */
  public DelimitedCodec(Codec<Buffer, IN, OUT> delegate) {
    this((byte) 10, true, delegate);

  }

  /**
   * Create a line-feed-delimited codec, using the given {@code Codec} as a delegate.
   *
   * @param stripDelimiter Flag to indicate whether the delimiter should be stripped from the
   *                       chunk or not during decoding.
   * @param delegate       The delegate {@link Codec}.
   */
  public DelimitedCodec(boolean stripDelimiter, Codec<Buffer, IN, OUT> delegate) {
    this((byte) 10, stripDelimiter, delegate);

  }

  /**
   * Create a delimited codec using the given delimiter and using the given {@code Codec}
   * as a delegate.
   *
   * @param delimiter      The delimiter to use.
   * @param stripDelimiter Flag to indicate whether the delimiter should be stripped from the
   *                       chunk or not during decoding.
   * @param delegate       The delegate {@link Codec}.
   */
  public DelimitedCodec(byte delimiter, boolean stripDelimiter, Codec<Buffer, IN, OUT> delegate) {
    super(delimiter);
    this.stripDelimiter = stripDelimiter;
    this.delegate = delegate;
  }

  @Override
  public Function<Buffer, IN> decoder(Consumer<IN> next) {
    return new DelimitedDecoder(next);
  }

  private class DelimitedDecoder implements Function<Buffer, IN> {
    private final Function<Buffer, IN> decoder;

    DelimitedDecoder(Consumer<IN> next) {
      this.decoder = delegate.decoder(next);
    }

    @Override
    public IN apply(Buffer bytes) {
      if (bytes.remaining() == 0) {
        return null;
      }

      Iterable<View> views = bytes.split(delimiter, stripDelimiter);

      int limit = bytes.limit();
      int position = bytes.position();

      for (Buffer.View view : views) {
        Buffer b = view.get();
        decoder.apply(b);
      }

      bytes.limit(limit);
      bytes.position(position);

      return null;
    }
  }

  @Override
  public Buffer apply(OUT out) {
    Buffer buffer = new Buffer();
    Buffer encoded = delegate.apply(out);
    if (null != encoded && encoded.remaining() > 0) {
      buffer.append(encoded).append(delimiter);
    }
    return buffer.flip();
  }

}
